1. Field of the Invention
The present invention relates to a surface inspection apparatus and a surface inspection method, which picks up images of a plurality of surfaces formed on a peripheral edge portion of a plate-like object, such as a silicon wafer, so that images of the plurality of surfaces can be obtained.
2. Description of the Related Art
In general, a peripheral edge portion of a plate-like object, i.e., a silicon wafer, includes a edge portions. The edge portions are formed between the circumferential surface and upper and lower plate surfaces of the silicon wafer. The edge portions are chamfered, because they are liable to be damaged due to external force applied thereto. Thus, the circumferential surface, and a first tapered surface and a second tapered surface formed by chamfering, exist in the peripheral edge portion of the silicon wafer.
If there is any defect, such as a nick, a crack, a small projection, or adhesion of particles, in the three surfaces formed in the peripheral edge portion of the plate-like object, a critical problem may arise in the silicon wafer. To avoid this, the chamfered silicon wafer is subjected to inspection whether there is any defect, such as a nick, a crack, a small projection, or adhesion of particles, in the three surfaces formed in the peripheral edge portion.
Conventionally, to inspect the peripheral edge portion of a silicon wafer, a surface inspection apparatus has been proposed, which picks up images of a plurality of surfaces of the peripheral edge portion, so that images of the plurality of surfaces can be obtained. Such conventional art is disclosed in, for example, Patent Documents 1 or 2 indicated below.
More specifically, the conventional surface inspection has first to third CCD cameras 10a, 10b and 10c as image pickup portions, as shown in FIG. 8. The peripheral edge portion of a disc-shaped silicon wafer 100 to be inspected includes the three surfaces of a circumferential surface 101a, an upper tapered surface 101b formed by chamfering the upper surface edge of the silicon wafer 100, and a lower tapered surface 101c formed by chamfering the lower surface edge of the silicon wafer 100.
The first CCD camera 10a is located in a position facing the circumferential surface 101a of the peripheral edge portion. The second CCD camera 10b is located in a position facing the upper tapered surface 101b. The third CCD camera 10c is located in a position facing the lower tapered surface 101c. 
In this state, the silicon wafer 100 is rotated about a center axis (not shown), so that the first to third CCD cameras 10a, 10b and 10c independently pick up images of the circumferential surface 101a, the upper tapered surface 101b and the lower tapered surface 101c of the peripheral edge portion of the silicon wafer 100.
As a result, the surface inspection apparatus separately obtains an image corresponding to the circumferential surface 101a based on an image signal output from the first CCD camera 10a, an image corresponding to the upper tapered surface 101b based on an image signal output from the second CCD camera 10b, and an image corresponding to the lower tapered surface 101c based on an image signal output from the third CCD camera 10c. 
These images are displayed in, for example, a monitor device. The inspector inspects whether there is any defect, such as a crack or adhesion of particles, in the peripheral edge portion based on the images corresponding to the circumferential surface 101a, the upper tapered surface 101b and the lower tapered surface 101c of the peripheral edge portion of the silicon wafer 100 displayed on the monitor device.
Patent Document 1: Jpn. Pat. Appln. KOKAI Publication No. 2003-139523
Patent Document 2: Jpn. Pat. Appln. KOKAI Publication No. 2003-243465